WEDNESDAY, June 13 , 2001 (HealthDayNews) -- Old age was spotted as a risk factor for complications or death from West Nile virus when the disease first appeared in the United States in 1999. Now, a new study says so is diabetes.
Denis Nash, an epidemiologist at the Centers for Disease Control and Prevention (CDC), says his findings should give doctors a better sense of the course of West Nile fever and which patients are most likely to go to the hospital or to die.
Diabetics of any age had 5.1 times the risk of death than people without the blood sugar condition. Why that's true isn't clear, Nash says, but diabetics, particularly elderly ones, may have weaker immune systems that leave them vulnerable to more severe bouts of infection. "That's just a hypothesis right now," he says.
Nash is lead author of the study, which appears this week in The New England Journal of Medicine. His study of the 1999 outbreak shows that people over age 50 were at least five to 10 times more likely to contract West Nile as younger patients. For those 70 or older, who made up about 50 percent of the cases, the rate of infection was roughly 33 times higher than people in their teens or younger. The outbreak killed seven New York City-area residents and sickened more than 50 others.
West Nile fever appeared suddenly in New York City. In August and September 1999, 59 cases were confirmed after initial confusion about the strain of virus involved, and seven people (12 percent) died. The median age for the 59 people was 71 years. Roughly six in 10 West Nile patients got encephalitis (an inflammation of the brain) and 27 percent developed severe muscle weakness. Ten percent were partially paralyzed due to nerve damage.
The elderly were hit hardest by the infection, which also can cause spinal column meningitis, an inflammation of the membranes that surround the spine. People 75 or older without diabetes had an 8.5-fold higher risk of dying from West Nile than younger patients.
Nash says whether age or disease is a factor, "physicians should be more aware that their patients [with encephalitis] might be exposed to West Nile virus. It may be the first time that a public health department hears about it in their jurisdiction."
Ideally, officials would detect the virus in mosquitoes or birds before a human case cropped up, but that's not always possible, Nash says.
While West Nile fever had occurred in other countries, including Israel and Romania, the outbreak two years ago in New York was the first time the disease was detected in the United States. And while surveillance and mosquito-eradication efforts have dramatically cut the number of cases since 1999, researchers say doctors in the Eastern United States should stay alert for clusters of unusual infections that might signal a new outbreak.
"The data indicate that it was more than just a one-year fluke thing. It does look like the virus is here to stay," says Dr. Kenneth Tyler, a neurologist at the University of Colorado Health Sciences Center in Denver and author of an editorial accompanying the journal article. "This is going to be a cause of encephalitis in a widening geographic area in the United States for the foreseeable future."
After its debut on the East Coast, West Nile has been driven into something of a remission. For example, in New York State, the heaviest hit region in 1999, health officials reported 14 cases and one death in 2000. In New Jersey, six people contracted the disease in 2000 and one died, while in Connecticut only one case was confirmed.
So far this year, only one infected bird has been found in New York and no human cases have been reported. Through early June, officials say the density of dead crows, thought to reflect the presence of the mosquito-borne viral disease, has been almost uniformly low, with the exception of Rockland County, north of New York City.
Yet Rockland County, which has experienced moderate die-off of birds so far this year, has an unusually large population of roosting crows, which may skew the results of surveys, says Kristine Smith, a spokeswoman for the New York State Department of Health in Albany.
Meanwhile, New Jersey officials report many more cases of avian West Nile this year, with a dozen crows in Bergen, Middlesex and Monmouth Counties infected with the organism.
The virus has been identified as far north as Vermont and as far south as North Carolina, and researchers believe it could spread wherever its preferred transportation, the Culex pipens mosquito, calls home.
The disease's historical pattern has been to strike birds and small mammals first, then spread to humans and larger beasts as the summer wears on. "Anything that can be done earlier to interrupt this cycle" can help prevent infections in people, Smith says.
While the 1999 outbreak prompted mass mosquito spraying, New York has no plans for a similar assault on the pests this year. Rather, Smith says the state will use strategic doses of larvicides to kill the insects' young and is encouraging residents to remove mosquito-friendly habitats, particularly basins of standing water, to keep the insects from proliferating. If the infection surges, the sprayers might return, she says.
What To Do
For more about West Nile, try this Web site dedicated to the disease. You also can get information on the infection by visiting the CDC. To read more on how the virus might affect horses, livestock, poultry and wildlife, check information provided by the U.S. Department of Agriculture.
Or, read previous HealthDay articles on the West Nile virus.
